In recent years, a great variety of electrical appliances have become available for operation by the low voltage power of direct-current electrical systems found in vehicles. Such appliances are generally interconnected to the electrical system by use of an adapter plug or connector, which is inserted into a cigarette lighter socket or receptacle. Electrical appliances and accessories that can be operated from a vehicle electrical system include battery chargers, portable televisions, cellular phones and the like. Demand for portable electronic devices makes it quite desirable to provide such appliances with a cigarette lighter adapter (CLA) to give users the option of powering these devices with the automotive electrical system.
Important qualities in CLAs designed for consumer use are ease, speed and reliability of manufacturing in addition to an end product that is sturdy and resists tampering by the consumer. CLAs that are easily disassembled by the consumer create problems including safety risks, difficulty in making requested repairs, and uncertainty in determining cause of defects. For example, a CLA that may be easily disassembled increases the probability that the consumer will attempt to repair or modify the device, which could lead to wiring misconnections and other safety concerns. An easily disassembled CLA also increases the probability that a part will be lost. Finally, if the consumer is able to disassemble the device, it can be impossible to determine the nature of the fault since the consumer may have altered the CLA's configuration before returning it for repair.
The prior art offers a number of ways to manufacture CLAs, but all suffer from certain disadvantages. For ease of manufacture and economy, CLAs are usually made from thermoformed plastics. Generally, the CLA comprises two halves that house the wiring components and electrical contacts. Simple methods for securing these two halves include using screws or configuring the parts so that they snap fit. However, the use of screws increases the manufacturing time, snap fit connections are relatively weak, and both systems are easily disassembled by the user. Anti-backout screws may be used to prevent disassembly, but still increase the time of manufacture and are expensive. Additionally, the configuration of the CLA makes it difficult to provide screw locations in the barrel due to space considerations and the possibility of shorting out the electrical connections.
An alternative strategy involves gluing the halves together. While such CLAs have the advantage of being tamper resistant, the curing time of the adhesive dramatically slows the manufacturing process. Moreover, quality control issues are exacerbated as gluing can often result in poor cosmetic results. Ultrasonic bonding can provide better results, but it has been found that bonding small, cylindrical objects is difficult. Indeed, attempts to use ultrasonic bonding in the manufacture of CLAs have resulted in a success rate of less than 50%, which is obviously unacceptable.
Finally, other known means of securing the pieces of a CLA have proven deficient for various reasons. For example, screw-on tips have been used to secure the CLA pieces, but the means of attachment is easy to disassemble and the screw-on tip can be lost. External collars have also been used, but they also can be easy to remove. Further, they are not compatible with flat-nosed CLAs that interface with the securing springs of modern cigarette lighters.
Accordingly, there is a need for a process of manufacturing CLAs that is fast and economical. There is also a need for producing CLAs that resist disassembly by the user in order to maximize safety and reliability. This invention satisfies these and other needs.